PGD in female carriers of balanced Robertsonian and reciprocal translocations by first polar body analysis.

Abstract

Preimplantation genetic diagnosis (PGD) using the first polar body (1PB) is a modality of PGD that can be used when the woman is the carrier of a genetic disease or of a balanced chromosomal reorganization. PGD using 1PB biopsy in carriers of balanced chromosome reorganizations has not become generalized. Here, we describe our experience based on the analysis of unfertilized or fresh, non-inseminated control oocytes, by fixing separately the 1PB and the corresponding oocyte, and on the study of six clinical cases of PGD using 1PB biopsy (four Robertsonian translocations and two reciprocal translocations). In fresh oocytes, the chromosome morphology of the 1PB was well preserved, and the results were always concordant for each oocyte-1PB pair. This indicates that the 1PB can be reliably used for the diagnosis of chromosome reorganizations. In these studies the technical problems encountered when performing PGD using 1PB biopsies for chromosome studies are also addressed. Three different strategies of 1PB biopsy (laser beam, partial zona dissection and acid Tyrode's) and two different protocols (intracytoplasmic sperm injection before or after 1PB biopsy) and their effect on the percentage of oocytes diagnosed and the fertilization rate, are discussed. In reciprocal translocation cases, published in the literature or studied by us, in which at least nine oocytes had been diagnosed, a correlation has been found between the frequency of nondisjunction observed and the theoretical recombination rate. To date, PGD by 1PB analysis alone or combined with blastomere biopsies in female carriers of chromosomal rearrangements has been used in 18 cases, with a further six cases reported here. A total of 325 cumulus-oocyte complexes have been obtained, of which 294 were biopsied and 224 were diagnosed. A total of 52 embryos was transferred, 19 of which implanted and 17 produced full-term pregnancies.